Agent for protecting the surface of lithographic printing plate

Claim 2

A process for gumming a lithiographic printing plate having a hydrophilic non-image area and a lipophilic image area which comprises the steps of: (a) preparing a protective agent comprising an aqueous phase having dissolved therein a film-forming hydrophilic high molecular weight compound for protecting the non-image area and an oil phase containing a water-insoluble organic solvent and a surfactant, wherein said surfactant is comprised of an alkylphenyl type nonionic surfactant represented by the general formula (I) ##STR2## where R is an alkyl group, p is 1 or 2, m is an integer of 1 to 4 and n is an integer of 2 or more, the surfactant having an HLB less than 14 and a sodium salt of a dialkylsulfosuccinate; and (b) coating a plate with said emulsion-type protective agent.

Claim 3

The process of claim 1, wherein said alkylphenyl nonionic surfactant is selected from the group consisting of a polyoxymethylene octylphenyl ether, a polyoxymethylene nonylphenyl ether, a polyoxymethylene cetylphenyl ether, a polyoxymethylene laurylphenyl ether, a polyoxyethylene octylphenyl ether, a polyoxymethylene nonylphenyl ether, a polyoxyethylene decylphenyl ether, a polyoxyethylene laurylphenyl ether, a polyoxypropylene octylphenyl ether, a polyoxypropylene nonylphenyl ether, a polyoxypropylene decylphenyl ether, a polyoxypropylene laurylphenyl ether, a polyoxypropylene cetylphenyl ether, a polyoxybutylene octylphenyl ether, a polyoxybutylene nonylphenyl ether, a polyoxybutylene decylphenyl ether, a polyoxybutylene laurylphenyl ether, a polyoxybutylene cetylphenyl ether, and a polyoxyethylene dinonylphenyl ether all having an HLB less than 14.

Claim 4

The process of claim 1, wherein said alkylphenyl nonionic surfactant is polyoxyethylene nonylphenyl ether or polyoxyethylene octylphenyl ether.

Claim 5

The process of claim 1, wherein said dialkylsulfosuccinate is selected from the group consisting of sodium dihexylsulfosuccinate, sodium di(2-ethylhexyl)sulfosuccinate, sodium dinonylsulfosuccinate and sodium dilaurylsulfosuccinate.

Claim 6

The process of claim 1, wherein the total amount of said nonionic and said anionic surfactant is about 0.5 to about 10 weight % based on the weight of the plate protective agent.

Claim 7

The process of claim 1, wherein the proportion of said nonionic surfactant to said anionic surfactant is about 10:1 to 1:10.

Claim 8

The process of claim 1, wherein said organic solvent is a plasticizer which solidifies at a temperature less than 15° C. and boils at a temperature higher than 300° C. at atmospheric pressure.

Claim 9

The process of claim 1, wherein said organic solvent is a solvent insoluble in water.

Claim 10

The process of claim 1, wherein said solvent is present in an amount of about 0.1 to 10 weight % based on the weight of the surface protective agent.

Claim 11

The process of claim 1, wherein said oil phase additionally contains a lipophilic substance which enhances the stability of the emulsion.

Claim 12

The process of claim 1, wherein said hydrophilic compound is selected from the group consisting of dextrin, gum arabic, an alginate, a water soluble cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, an acrylamide copolymer, vinylmethyl ether-maleic anhydride copolymer, and vinyl acetate-maleic anhydride copolymer.

Claim 13

The process of claim 11, wherein said hydrophilic compound is selected from the group consisting of gum arabic, dextrin, polyvinyl pyrrolidone, carboxymethyl cellulose and polyvinyl alcohol.

Claim 14

The process of claim 12, wherein said hydrophilic polymer is gum arabic.

Claim 15

The process of claim 1, wherein said hydrophilic high molecular weight compound is present in an amount of about 5 to 40 weight % based on the weight of the surface protective agent.

Claim 16

The process of claim 1, wherein said aqueous phase additionally contains a wetting agent.

Claim 17

The process of claim 1, wherein said wetting agent is a polyhydric alcohol.

Claim 18

The process of claim 1, wherein said aqueous phase additionally contains a water soluble salt.

Claim 19

The process of claim 1, wherein said alkylphenyl nonionic surfactant has an HLB in the range of from 4 to 12.

Claim 20

The process of claim 18, wherein said alkylphenyl nonionic surfactant has an HLB in the range of from 7 to 12.

Claim 21

The process of claim 19, wherein the total amount of said nonionic and said anionic surfactant is about 0.5 to about 10 weight % based on the weight of the plate protecting agent.

Claim 22

The process of claim 20, wherein the proportion of said nonionic surfactant to said anionic surfactant is about 10:1 to 1:10.

Claim 23

The process of claim 21, wherein said proportion is 5:1 to 1:5.

Claim 24

The process of claim 22, wherein said water-insoluble organic solvent is a plasticizer which solidifies at a temperature less than 15° C. and boils at a temperature higher than 300° C. at atmospheric pressure.

Claim 25

The process of claim 23, wherein said plasticizer is present in an amount of about 0.1 to 10 weight % based on the weight of the surface protective agent.

Claim 26

The process of claim 24, wherein said oil phase additionally contains a lipophilic substance which enhances the stability of the emulsion and minimizes the potential decrease in the lipophilicity of said image area.

Claim 27

The process of claim 25, wherein said lipophilic substance is selected from the group consisting of a novolac phenolic resin, rosin and modified rosin.

Claim 28

The process of claim 25, wherein said lipophilic substance is an aliphatic carboxylic acid having 5 to 25 carbon atoms or castor oil.

Claim 29

The process of claim 27, wherein said aliphatic carboxylic acid is oleic acid, lauric acid, valeric acid, nonylic acid, capric acid, myristic acid or palmitric acid.

Claim 30

The process of claim 25, wherein said lipophilic substance is present in an amount from about 0.05 to about 5 weight % based on the total weight of the protective agent.

Claim 31

The process of claim 29, wherein said lipophilic substance is present in an amount from 0.1 to 1 weight % based on the total weight of the protective agent.

Claim 32

The process of claim 25, wherein said film forming hydrophilic high molecular weight compound is selected from the group consisting of gum arabic, dextrin, polyvinyl pyrrolidone, carboxymethyl cellulose and polyvinyl alcohol.

Claim 33

The process of claim 31, wherein said film forming hydrophilic high molecular weight compound is gum arabic.

Claim 34

The process of claim 31, wherein said film forming hydrophilic high molecular weight compound is a combination of gum arabic and dextrin.

Claim 35

The process of claim 31, wherein said film forming hydrophilic high molecular weight compound is present in an amount from about 5 to 40 weight % based on the total weight of the protective agent, and in an amount from about 6 to about 60 weight % in the aqueous phase.

Claim 36

The process of claim 31, wherein said aqueous phase additionally contains a polyhydric alcohol which is selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentane diol, hexylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, glycerin, sorbitol and pentaerythritol.

Claim 37

The process of claim 35, wherein said polyhydric alcohol is glycerin.

Claim 38

The process of claim 35, wherein said polyhydric alcohol is present in an amount from about 0.5 to about 10 weight % based on the total weight of the protective agent.

Claim 39

The process of claim 32, wherein said aqueous phase has a pH from 1 to 5.

Claim 40

The process of claim 38, wherein said aqueous phase has a pH from 1 to 3.

Claim 41

The process of claim 39, wherein said aqueous phase contains phosphoric acid.

Claim 42

The process of claim 40, wherein said phosphoric acid is present in an amount of from 0.1 to 8 weight % based on the total weight of said aqueous phase.

Claim 43

The process of claim 41, wherein said phosphoric acid is present in an amount of from 0.5 to 5 weight % based on the total weight of said aqueous phase.

Claim 44

The process of claim 42, wherein said aqueous phase additionally contains a water soluble salt selected from the group consisting of water-soluble alkali metal salts and ammonium salts of acetic acid, molybdic acid, boric acid, nitric acid, sulfuric acid, phosphoric acid and polyphosphoric acid.

Claim 45

A process for preparing a printing plate which comprises exposing and developing a printing plate forming material and coating the plate with an emulsion type protective agent comprising an aqueous phase having dissolved therein a film-forming hydrophilic high molecular weight compound for protecting the non-image area and an oil phase containing a water-insoluble organic solvent and a surfactant represented by the general formula (I): ##STR3## where R is an alkyl group, p is 1 or 2, m is an integer of 1 to 4 and n is an integer of 2 or more, the surfactant having an HLB less than 14 and a sodium salt of a dialkylsulfosuccinate surfactant.

Claim 46

A process for preparing a printing plate which comprises exposing and developing a printing plate forming material and coating the plate with an emulsion type protective agent comprising an aqueous phase having dissolved therein a film-forming hydrophilic high molecular weight compound for protecting the non-image area and an oil phase containing a water-insoluble organic solvent and a surfactant represented by the general formula (I): ##STR3## where R is an alkyl group, p is 1 or 2, m is an integer of 1 to 4 and n is an integer of 2 or more, the surfactant having an HLB less than 14 and a sodium salt of a dialkylsulfosuccinate surfactant.